Refrigerant control to maintain minimum head



United States Patent 3,405,536 REFRIGERANT CONTROL TO MAINTAIN MINIMUM HEAD James W. Endress, Syracuse, N.Y., assignor to Carrier Corporation, Syracuse, N.Y., a corporation of Delaware Filed Oct. 28, 1966, Ser. No. 590,301 3 Claims. (Cl. 62-218) ABSTRACT OF THE DISCLOSURE A refrigerant flow control for regulating the passage of refrigerant from the high side of a refrigeration system to the low side of the system in response to the height of a column of liquid refrigerant. The control provides a minimum pressure differential between the high and low pressure sides of the system proportional to the height of the refrigerant column sufficient to assure a supply of liquid refrigerant to the refrigeration system compressor-motor to prevent the motor from overheating.

This invention relates to a refrigeration machine. More particularly this invention relates to refrigerant flow in a refrigeration machine. Still more particularly, this invention relates to a refrigeration machine with provisions for supplying refrigerant to the refrigerant compressor motor to provide cooling thereof.

In a centrifugal refrigeration machine driven by an electric motor, it is desirable to utilize refrigerant to cool the motor to prevent overheating thereof. Numerous methods have been devised to provide a supply of refrigerant to the motor. One of the most economical and sim plest methods is to provide a liquid refrigerant supply line between the motor and the refrigerant condenser and a gaseous refrigerant return line from the motor to the evaporator. Under normal operating conditions, the pressure differential existing between the condenser and evaporator is sufiicient to provide adequate flow of refrigerant through the motor for cooling. However, at start-up or under abnormal operating conditions wherein there is a low pressure differential between the high and low sides of the machine, an insufiicient flow of refrigerant to the motor results causing overheating thereof.

It is therefore the chief object of this invention to provide an improved refrigerant flow control means for a refrigeration machine.

It is another object of this invention to provide a re frigerant flow control means for a refrigeration machine which will maintain a sufficient pressure differential between the high and low pressure sides thereof to insure an adequate refrigerant supply to the motor for cooling thereof.

The objects of this invention are attained by providing a motor driven refrigeration machine with a refrigerant collecting chamber disposed above the drive motor with a standpipe communicating between the collecting chamber and the high pressure side of the system so that liquid refrigerant will be forced into the collecting chamber under normal operating conditions. A refrigerant line between the collecting chamber and the motor provides refrigerant to the motor for cooling. Means are provided for maintaining a relatively constant refrigerant level in the collection chamber and for metering liquid refrigerant to the low side of the refrigeration machine.

Other objects and features of my invention will be apparent upon a consideration of the ensuing specification and drawings in which the figure is a diagrammatic view with parts in section of a motor driven centrifugal refrigeration machine employing the flow control apparatus of my invention.

Referring more particularly to the drawing, there is Patented Oct. 15, 1968 shown a refrigeration machine 1, similar to the machine disclosed in United States Letters Patent No. 3,270,517, issued Sept. 16, 1966, to William E. Clark, having a motor-compressor 3, a condenser 5 and an evaporator 7. A first refrigerant collection chamber 9 is in communication with condenser 5 by means of passageway 11. A second refrigerant collecting chamber 13 communicates with chamber 9 through standpipe 15. A valve 17 in chamber 9 operably connected to a float 19 in chamber 13 by a rod 21 in standpipe 15 regulates the flow of refrigerant into evaporator 7 responsive to the refrigerant level in chamber 13. A tube bundle 6 is provided in condenser 5 for passing a heat exchange medium therethrough such as water from a cooling tower (not shown) to cool the compressed refrigerant from motor compressor 3 causing it to condense, the liquid refrigerant filling chamber 9, standpipe 15, partially filling chamber 13 and collecting as a pool in the bottom of condenser 5. A tube bundle 8 in evaporator 7 is provided for passing the medium to be cooled in heat transfer relation with the refrigerant expanded through valve 17.

A motor cooling refrigerant supply line 23 having a flow control orifice 25 therein provides liquid refrigerant from chamber 13 to the motor-compressor for cooling the motor. Some of the liquid refrigerant in the motor, after absorbing the heat from the motor will vaporize, and is discharged with excess liquid through motor cooling refrigerant drain line 27 to evaporator 7.

A vent line 10 between the top of chamber 13 and the motor-compressor 3 is provided for venting noncondensables from chamber 13 through the motor compressor so that they will eventually reach the condenser and be withdrawn from the machine. An orifice 12 is provided in line 10 to minimize flow therethrough and to prevent equalization of pressure between chamber 13 and the motor compressor.

For a description of refrigerant distribution within the motor, reference may be had to United States Letters Patent No. 3,241,331, issued Mar. 22, 1966, to Endress et al.

With this arrangement under normal operating conditions, the pressure differential between the high and low pressure sides of the machine will cause liquid refrigerant to rise in standpipe 15 and partially flood chamber 13. Stated another way under normal operating conditions, the condenser is under a relatively high pressure. The pressure in chamber 13 is somewhat lower than condenser pressure due to the fact that the chamber is in communication with the low pressure evaporator through the motor cooling circuit comprised of line 23, the motor 3 and line 27. Since there is a higher pressure on the pool of refrigerant in the condenser than there is at the top of standpipe 15, condenser pressure will force refrigerant liquid up standpipe 15 into chamber 13.

As can be seen from the foregoing, in the event of temporary abnormal operating conditions of the refrigeration machine resulting in a pressure differential insufficient to raise refrigerant to the level of chamber 13, the liquid refrigerant level in condenser 5 will rise and due to the termination of flow of liquid refrigerant to chamber 13, float 19 will drop, closing valve 17.

Under these conditions, the quantity of liquid refrigerant in the condenser will increase, flooding a portion of the tubes therein which in turn will cause an increase in the condensing temperature. The simultaneous removal of refrigerant from the evaporator by the compressor in the absence of a refrigerant supply thereof will lower evaporator pressure, the resulting evaporator and condenser conditions increasing the system pressure differential to the desired minimum level. This will force refrigerant higher into chamber 13 until refrigerant flow 3 through the machine is again controlled by valve 17 and float 19. v i I I While I have described a preferred embodiment of my invention, it is to be understood that the invention is not limited thereto but may be otherwise embodied within the scope of the following claims.

I claim:

1. A refrigerant flow control apparatus for a motorcompressor refrigeration machine having a refrigerant condenser and a refrigerant evaporator therein comprising a first refrigerant collecting chamber for collecting liquid refrigerant from the condenser, a second refrigerant collecting chamber disposed above the motorcompressor, means communicating between said first and said second collecting chambers to provide a column of liquid refrigerant therebetween, refrigerant metering means directly responsive to the level of refrigerant in said second refrigerant collecting chamber for regulating the flow of refrigerant from said first refrigerant collecting chamber to said evaporator and means for providing refrigerant from said second refrigerant collecting chamber to the motor-compressor for cooling the motor thereof.

2. A refrigerant flow control apparatus according to claim 1 wherein said refrigerant metering means comprises a valve disposed in said first refrigerant collecting chamber for regulating the flow of refrigerant from said first chamber to the evaporator, a float disposed in said second refrigerant collecting chamber, and means operably connecting said float to said valve for regulating the flow of refrigerant to the evaporator responsive to the level of the refrigerant in said second refrigerant collecting chamber.

3. A refrigerant flow control apparatus according to claim 1 wherein said means for providing refrigerant to the compressor-motor comprises a refrigerant line communicating between the bottom of said second refrigerant collecting chamber and the motor for passage of refrigerant therebetween and restriction means disposed in said refrigerant line for restricting flow of refrigerant to the motor.

References Cited UNITED STATES PATENTS 3,165,905 1/1965 Ware 62-505 XR MEYER PERLIN, Primary Examiner. 

